1. Field of the Invention
This invention relates to a buckling restrained brace, and more particularly to a buckling restrained brace that is formed with grooves for engaging respectively connecting plates of a framework of a building.
2. Description of the Related Art
Buckling restrained braces are used in a steel framework of a building for absorbing vibration energy generated by an earthquake, to delay the damage of the framework resulting from the shock of the earthquake, and to break prior to breakage of the parts of the framework coupled to the buckling restrained braces. In general, current buckling restrained braces can be classified into the following three types:
1. Single-tube and single-core type. Referring to FIGS. 1 and 2, a single-tube and single-core type buckling restrained brace 6 includes an axial member 61 and a restraining unit 62. The axial member 61 has a middle section 611 of a cross-shaped cross-section, and two coupling sections 612 connected respectively to two ends of the axial member 61. The restraining unit 62 includes a steel tube 621 disposed around the axial member 61, and a concrete material 622 filling a space between the axial member 61 and the steel tube 621.
Referring to FIG. 3, each of the coupling sections 612 of the axial member 61 is connected fixedly to a connecting plate 7 of the framework by a coupling unit. The coupling unit includes a plurality of abutment plates 71 (only two are shown) and a plurality of bolts 72. Such connecting process is time-consuming.
2. Single-tube and Dual-core type. Referring to FIGS. 4 and 5, a single-tube and dual-core type buckling restrained brace 8 includes an axial member 81 and a restraining unit 82. The axial member 81 includes two elongated steel plates 811 parallel to each other. The restraining unit 82 includes a steel tube 821 and a concrete material 822 filling spaces among the steel tube 821 and the steel plates 811.
With further reference to FIG. 6, each end of the axial member 81 is connected fixedly to a connecting plate 7′ by two bolts 72′. The steel plates 811 are spaced apart from each other by a distance (d) to define two grooves 812 at the ends of the axial member 81. Each of the connecting plates 7′ is fixed within the corresponding groove 812 and between the steel plates 811 by the bolts 72′. The connecting plate 7′ has a thickness (t).
This type of buckling restrained braces suffer from the following disadvantages:                (1) High manufacturing precision is required to allow the connecting plates 7′ to engage respectively and fittingly the grooves 812. In case the thickness (t) is greater than the distance (d), the connecting plates 7′ cannot be inserted into the steel plates 811. In case the thickness (t) is smaller than the distance (d), the connecting plates 7′ cannot be fixed between the steel plates 811.        (2) Since the steel plates 811 are parallel to the connecting plates 7′, when subjected to a force resulting from an earthquake in a direction perpendicular to the connecting plates 7′, buckling of the steel plates 811 easily occurs.            3. Dual-tube and dual-core type. Referring to FIGS. 7 and 8, a dual-tube and dual-core type buckling restrained brace 9 includes a pair of first and second supporting units 91, 92, each of which is similar in construction to the single-tube and single-core type buckling restrained brace 6 (see FIG. 2). Each of the supporting units 91, 92 includes an axial member 911, 921, and a restraining unit 912, 922. Unlike the single-tube and single-core type buckling restrained brace 6 (see FIG. 2), the axial members 911, 921 have a T-shaped cross-section.
With further reference to FIG. 9, to interconnect the dual-tube and dual-core type buckling restrained brace 9 and a connecting plate 7″, the connecting plate 7″ is first sandwiched between an adjacent pair of parallel plate portions of the axial members 911, 921, and is subsequently locked between the same by a plurality of bolts 72″. Thereafter, two steel plates 93 are welded to the restraining units 912, 922.
Since the axial members 911, 921 are T-shaped in cross-section, when subjected to a force resulting from an earthquake in a direction perpendicular to the connecting plate 7″, buckling of the steel plates 811 can be reduced. Furthermore, the connecting plate 7″ can be fixed effectively to the axial members 911, 921 due to the fact that the connecting plate 7″ can be clamped between the adjacent pair of parallel plate portions of the axial members 911, 921 prior to welding of the steel plates 93 thereto. However, the dual-tube and dual-core type buckling restrained brace 9 has a drawback. That is, due to inclusion of two supporting units 91, 92 in the dual-tube and dual-core type buckling restrained brace 9, a substantial amount of the steel material is required to form the axial members 911, 921 and the tubes of the restraining units 912, 922.